The BMW diesel engine is equipped with a turbocharger. In the turbocharger, two wheels, turbine and compressor, are located on one shaft, which are located in housings separated from each other. The exhaust gases are used to drive the turbine wheel. They accelerate the shaft to a speed of 120,0001 /min. Since the wheels have a common rotor, the compressor wheel rotates at the same speed and pumps fresh air into the engine cylinders.
Thanks to the high fill factor in existing engines, power gains of up to 100% can be realized. The increase in power depends on the boost pressure, which for passenger car engines is 0.4-0.8 bar (total boost pressure approx. 1.8 bar). If the boost pressure begins to exceed the value set by the factory, the bypass valve for part of the exhaust gases bypassing the turbine wheel opens, and the boost pressure decreases.
In addition to the engine power, the use of a turbocharger also increases the torque, which is above all desirable from the point of view of smooth engine operation. Compared to a petrol engine, a diesel engine does not need to reduce the compression ratio due to supercharging, so that the injected fuel is fully utilized even at low engine speeds.
The turbocharger is an extremely precisely manufactured unit. Therefore, in case of repair, it is recommended to contact a specialist. As a rule, if a defect occurs, the turbocharger is replaced as an assembly.
The turbocharger is lubricated with engine oil from the engine lubrication system. To ensure adequate lubrication of the turbocharger bearings, the following requirements must be observed.
Use only prescribed engine oils.
Running on too old engine oil can lead to coking of the turbocharger bearings. Therefore, the replacement of engine oil and oil filter must be carried out strictly in accordance with the maintenance card.
Since even the smallest particles of dirt can lead to the destruction of the turbocharger, never allow the engine to run without an air filter.